Standard filters have only a single media pack filtering in one direction only. These types of arrangements require the media pack to be supported against collapse in high pressure drop conditions. In these types of applications, the efficiency cannot be increased without a degradation in flow rate or increase in pressure drop. An increase in efficiency also causes the dirt holding capacity to decrease. In many applications, the media is within a steel can, which contaminates the steel for scrap and causes customers to get less than premium value for the scrap metal.
Improvements are desirable.